Alkaline cells

ABSTRACT

An alkaline cell in which a resin composition comprising a halogenated butyl rubber having styrenic resins and phenolic resins blended therein is used as an insulating gasket interposed between a metal case containing electricity-generating elements therein and a metal sealing plate sealing the open end of said metal case, whereby the leakage of an alkaline electrolyte solution to the outside of the case is effectively prevented.

United States Patent [eki et a1. 1 July 1, 1975 1 ALKALINE CELLS 2.891.595 6/1959 Kuntz 6161. 260/853 X I 2,941,975 6/1960 Minckler. Jr. et a1. 260/853 X 1751 Invemorsl 2 39 9" 2.962.480 11/1960 Borunsky 260 853 x H'Takata; Tosh") Shlmllu Dam), 2.965.621 12/1960 Serniuk et a1... 260/85.3 of Japan 3.437.611 4/1969 Macklin A A 1 260/3.3 y 3,533,970 10/1970 Mihara et a1. 260/13 X [73l Asslgnee. Matsush1ti1Electnc lndustnalCtL, 3,61586' [0/197] Braem H 136/133 X Japan 3.661.650 5/1972 Flynn 136/133 22 Filed: June 5 1973 3.723.184 3/1973 Stark et all 136/133 3.779.979 12/1973 Tsuchlya 260/853 X [21] Appl. No: 367,130

Primary Examiner-Allen B. Curtis 30 Foreign Appncation p Data Assistant Exam1'ner' l"homas A. Waltz I June 20 1972 Japan IIIIIIIIIIIIIIIIIIIIIIIIIIIII 4762224 Attorney. Agent. or Firm-Stevens. Davls. M1l1er &

Mosher [52] US. Cl. 136/133; 260/33; 260/853 H [51] Int. Cl.. H0lm 1/02 1 1 ABSTRACT [58] Field of Search 136/133? 260/11 H1 An alkaline cell in which a resin composition compris 260/737 ing a halogenated butyl rubber having styrenic resins I and phenolic resins blended therein is used as an insu- [56] References cued lating gasket interposed between a metal case contain- UNITED STATES PATENTS ing electricity-generating elements therein and a metal 2.072.069 2/1937 E1115 4. 260 331 x Sealing plate Sealing the p end of said metal case. 2.087.337 7/1937 Tomsicek ct al. 260/33 X whereby the leakage of an alkaline electrolyte solution 2.145.412 H1939 n ann 260/33 X to the outside of the case is effectively prevented. 2.287.388 6/1942 McManus et a1 215/328 2.290.132 7/1942 Swain 61 a1. 260/33 6 Clams, 3 Drawmg Flgures SHEET Pm mOEm FI'I'I'IZIETFMU ms 3 8 92 59 3 SHEET 2 FIG. 2

YIELDING ELECTROLYTE SOLUTION LEAKAGE(%I or O O PERCENTAGE OF NUMBER OF CELLS 0 IO 20 3O 4O AMOUNT OF STYRENIC RESIN (PHRI (WITH I5PHR OF PHENOLIC RESIN INCORPORATED) YIELDING ELECTROLYTE SOLUTION LEAKAGE ("/o) m: SHEET 3 F I G. 3

5 IO I5 20 25 AMOUNT OF PHENOUC RESIN (PHR) (WITH ZOPHR OF STYRENIC RESIN INCORPORATED) ALKALINE CELLS This invention relates to alkaline cells such as mercury cells and manganese dioxide-zinc alkaline cells. and provides alkaline cells comprising an improved in sulating gasket for sealing the cells. whereby the leakage of electrolyte solution is prevented and the storage characteristic of the cells is improved.

Alkaline cells generally comprise a case containing electrictiy-generating elements therein and serving simultaneously as one electrode terminal. a sealing plate sealing an open end of the cell and serving simultaneously as the other electrode terminal. and an insulating gasket interposed between the open end of the cell and the sealing plate for electrically insulating said case and said sealing plate from each other.

Most ofthe problems involved in this type of alkaline cell have been electrical shorting. corrosion of external equipments and lowering of the cell capacity which are caused by the outward leakage of the electrolyte solu tion during use or storage of the cell. The leakage of the electrolyte solution is attributable mainly to the material of the insulating gasket as well as to the sealing method.

For the insulating gaskets of this type of cell. there have been used chloroprene rubber. styrene-butadiene rubber. butyl rubber. isoprene rubber. rubber containing fluorine. polyethylene and polyamides.

Chloroprene rubber is excellent in respect of strength and elasticity. but is poor in sealing property and has the defect that it provides leakage of the electrolyte solution. substantially shortening the storage life of the cell.

Styrene-butadiene rubber is unsatisfactory in respect of resistance to alkali and provides electrical shorting or leakage of the electrolyte solution during use of the cell. lsoprene rubber, because of its high permeability to aqueous vapor. also provides leakage of the electrolyte solution and renders the storage life of the cell remarkably shortened.

Butyl rubber is not adapted for single use because it provides leakage of a large amount of electrolyte solution at the contacting portions of the case and sealing plate due to its large impact resilience and large permanent set factor. although it has a low permeability to aqueous vapor and provides less leakage of electrolyte solution thcrethrough. Flourinecontained rubber also has a large impact resilience and is unsatisfactory in its bonding property with metals.

Polyamides and polyethylene have high rigidities and no impact resilience. and are extremely poor in bonding property and compatibility with metals.

The present invention contemplates the provision of alkaline cells free of electrolyte solution leakage over an extended period of time and having a long storage life. by improving the conventional insulating gaskets of the materials described above.

B using the insulating gaskets of the invention. an alkaline cell capable of storage for an extended period of time can be obtained. owing to its excellent electrolyte leakage proventing effect.

FIG. 1 is a side elevational view of one form of alkaline cell. with the half portion shown in section;

FIG. 2 is a diagram showing the relationship between the amount of styrenic resin in a resin composition eonstituting an insulating gasket and the percentage of the number of cells yielding electrolyte solution leakage; and

FIG. 3 is a diagram similarly showing the relationship between the amount of phenolic resin in the resin com position and the percentage of the number of cells yielding electrolyte solution leakage.

Referring to FIG. 1, there is shown the construction of a typical alkaline cell. Reference numeral 1 desig nates a case of the cell which is made from a nickeL plated steel sheet and serves simultaneously as a posi' tive electrode terminal. Reference numeral 2 desig nates a positive electrode mixture compression-molded in the case 1, which. when the cell is a mercury cell. is mercury oxide incorporating about l0 percent by weight of graphite as a conductive material. Reference numeral 3 designates a zinc electrode formed by the compression-molding of a 50l50 mesh zinc powder which is previously amalgamated with about 10 percent by weight of mercury for preventing the corrosion by electrolyte solution. Reference numeral 4 designates an ion-permeable separator which prevents the selfconsumption of the fine particles of the positive electrode mixture suspending in the electrolyte solution. by contact with the negative zinc electrode 3. Reference numeral 5 designates an electrolyte solution retainer made of a porous fibrous material for retaining an alkaline electrolyte solution. Reference numeral 6 desig nates an inner sealing plate and 7 designates an outer sealing plate. These sealing plates are coupled together at the central portions thereof by electric welding. The inner sealing plate 6 is coated with a tin plating to improve the electrical connection with the negative zinc electrode 3, and the outer sealing plate 7 is coated with a nickel plating to prevent the corrosion by external air and serves simultaneously as a negative electrode terminal per se. Reference numeral 8 designates an insulating gasket interposed between the sealing plates 6. 7 and the case I to insulate them electrically and also to provide gas-tight sealing therebetween.

For the insulating gasket 8 of the alkaline cell described above. a material is advantageously used which satisfies such conditions that the insulation resistance is high and preferably higher than 10 S1 cm. that the material is highly elastic and has a high recovery and a low permanent set factor. and that the material has a low permeability to aqueous vapor and resistance to al kali.

None of the conventional materials described above have been satisfactory for these conditions. For in stance. butyl rubber has excellent electrical and physical properties. and particularly it has a small permeability to aqueous vapor which is highly advantageous in preventing an electrolyte solution from penetrating into a gasket made thereof. However. the alkaline elec trolyte solution leaks to the outside of the cell. not only through the gasket but also largely from the joint of the gasket and the cell case or sealing plate. Therefore. the leakage cannot be prevented completely by the gasket made of butyl rubber which has large impact resilience and permanent set factor.

The present invention has been achieved based on the discovery that resin compositions comprising a halogenated butyl rubber as the main constitutent and contaiing styrenic resins and phenolic resins blended therein are highly suitable as materials for insulating gaskets of alkaline cells. By using insulating gaskets made of such compositions. the leakage of an alkaline EXAMPLE 1 lot] parts by weight 50 parts by weight Butyl rubber Carbon black Stearic acid l part by weight Zinc oxide parts by weight Tetramethylthiuram 1 part by weight disulfidc An insulating gasket was formed by mixing the mate rials mentioned above in a Banbury mixer. kneading the mixture on a roll. charging the kneaded mixture in a metal mold and vulcanizing it for 20 minutes at a tern perature of 160T.

resin incorporated in the composition on the electro lyte solution leaking ratio ofthe cells when the amounts of the chlorinated butyl rubber and phenolic resin are fixed and are respectively I00 parts by weight and parts by weight. and FIG. 3 shows the effect ofthe phenolic resin incorporated in the composition on the electrolyte solution leaking ratio of the cells when the amounts of the chlorinated butyl rubber and styrenic resin are fixed and are respectively 100 parts by weight and parts by weight The leakage as determined by the alkali reaction occurring on litmus paper attached to the surface of each cell. The leaking ratio represents the percentage of the number of cells yielding electrolyte solution leakage.

EXAMPLE 4 The same effect can be obtained w hen brominated butyl rubber is used in lieu of chlorinated butyl rubber. As an example. an insulating gasket was made of the following composition by the same process as in Exam ple 3:

Broniinated butyl rubber lllt) parts by weight Styrenic resin parts by weight EXAMPLE 2 Phenol formaldehyde resin 13 parts by weight Carbon black 3!) parts by weight Chlorinated butyl rubber 100 parts by weight W 5 F g Carhon black 51) parts by eight Tstrumclhylthwwm Steai'ic acid I part by weight dlsulfide 1 part by weight Tetramethylthiuram disulfide l part by weight EXANlPLE 5 Zinc xidc 4 weigh 30 The same effect was obtained by using styrenehutadi- A l k d f [h ene copolymers in lieu of the styrenic resin used in Exw co 051 i d n 2 fi d5 ma 8 O amples 3 and 4. In this case. it is preferable to use co- 1 v e same rocess as in xam e escn E l 0 e p p olvmers coiitainin i more than 80 ercent of st 'rene.

. 3 EXAMPLE 3 18 because excessively large proportions of butadiene in 5 t I l k d l f h i the composition will have adverse affects on the charw x s y ti i e wi i I S acteristics of the cell.

w i c composl 10115 3 O n d e Compnsmg, Grind E: A preferred example of the composition comprising butvl rubber and varying amounts of styrenic resin and y y styrene-butadiene copolymer is given below. phenol formaldehyde resin. by mixing the ingredients ofeach composition in a Banbury mixer to obtain a ho- (:hlm'mfll "5") whim i y g Sty rene-butatliene mogeneous mixture. kneading the mixture on an open mpnhmcr My h roll. aging the kneaded mixture for about 30 minutes. eight of styrene and 23 parts by eight charging the aged mixture in a metal mold upon cutting Sa t f U Ll ICllC it into a predetermined size. heat-treating the charged Phcml formdldchydu mixture for 5 minutes at a temperature of lC.. re- 45 resin l5 parts by weight moving the molded gasket from the metal mold after i 'f' 9' I H l d d h h SKLttIIC acid 2 parts by weight the metal mold was coo e an trimming t e urre Lintmidc 3 mm h} eight from If? gasket. Magnesium oxide 2 parts by weight Table l Mixing ratio (part by weight) SampleNo t!) I2) (3) (4] if (7i (8) cs! lltl] llil (12 H3) Chlorinated butyl rubber too too Hill ltlll loo iou ion loo loo ion loo ion lilo Styrenic resin 5 lo 5 2o 35 l 5 4o 20 1o 3a 3o 3 Phenol formaldehyde resin E5 l5 l5 E5 E5 l. l5 15 ll 5 ill I 25 Carbon black 3U 30 3U 3U 3U 3'1 ,1!) 1U 3U 31) t! ll] Zinc oxide 4 4 4 4 4 -l a 4 .1 4 4 i y i i a 2 i 3 1 2 2 2 a 2 1 Magnesium oxide Using the insulating gaskets of each composition thus made. 100 mercury cells of the construction shown in FIG. I and having a diameter of 15.6 mm and a hei 1' of 6.0 rnm ere produced. and the cells were preserved for days in a humid environment ofa humidity of o Fr RH or higher. to examine the degree of leakage ol alkaline electrolyte solution. The results are shown in FIGS. 2 and 3. FIG. 2 shows the effect of the styrenic An insulating gasket was made by processing the above composition in the same manner as in Example Phenolic resin is effectively used as an additive to the lialtxglcnated butyl rubber as stated previously. but it \i as found that a similar effect can be obtained by using modified phenolic resins. Namely. \yleneanodified phenol formaldehyde resin and melamine-modified phenol formaldehyde resin are also effectively used. Examples of the compositions comprising such compounds will be given below:

EXAMPLE 6 Chlorinated hulyl ltlil parts b weight rubber Styrene-hutadienc copolymer (8H 'A' by weight of styrene and 2t) )9 by eight of hutadienel '13 parts by weight Melamine-modified phenol formaldehyde l parts by eight resin Stearic acid 2 parts by weight Zinc oxide 6 parts by weight Table 2 Intrinsic Impact Compres Aqueous Weight Tensile \olumc resilience sive \apor reduction strength Example resisfactor permanent permeability ratio in Hardness tivity (3%) set factor factor X alkali (kg/cm) lI-em (5%) ll) gcm/ l%) cm sec cmHg Measuring ASTM ASTM ASTM ASTM CUP ASTM ASTM method D-257 D l 054 D-4 l 2 method D 4 l 2 D-4l 2 l l.()2 l(l 63.5 l3.5 l4.4 (L52 85.0 95 2 (\XUXH) 58.8 l7.5 [55 (L47 79.3 82 3 7.95Xlll 76.6 7.3 ll] (L40 180.5 73 4 8.75Xl0' 75.8 6.5 l 1.6 (L37 1950 7] S 7,5(lX l 0" R I .2 4.9 l'lll (1.35 205.5 70 6 8.86Xlll 35.5 3.8 lt).5 (1.4] 220.5 71 7 'vllSXlll 79.8 4.6 9.8 0.30 205.0 68 8 LOZXIU' 76.5 5.5 7.6 (L31 203.0 65

Alkyl phenol P by The test samples used for measuring these properties Carbon black parts by \velght v I d f h h r Steam. ml 2 parts weight vxere respectively ma e o t e compositions s own in Zinc oxide (1 parts by weight the Examples given above by the methods specified in Magnesium oxide l part by weight An insulating gasket was made by processing the above composition in the same manner as in Example 2 EXAMPLE 7 23 parts by eight I5 parts by weight 2 parts by eight 6 parts by weight l part by weight An insulating gasket was made by processing the above composition in the same manner as in Example 1 EXAMPLE 8 Chlorinated hutyl rubber St renc-lmtadienc eopolymer (til) 4 b eight of styrene and Ill by eight of butadiencl llltl parts by weight 2} parts by eight ASTM. and the measurements were taken according to the methods also specified in ASTM. The weight reduction ratios of alkali were determined by immersing each sample of a size of 5 X 5 X 0.l cm in a 20 percent by weight potassium hydroxide aqueous solution for 24 hours and thereafter measuring the weight reduction.

The gasket materials of the invention shown in Examples 3-8, as compared with the conventional gaskets shown in Examples 1 and 2. have large impact resilience factors and small compressive permanent set factors. and hence. have excellent packing characteristics, and further, they have small aqueous vapor permeability factors. Therefore. the gasket materials of the invention are effective for the prevention of electrolyte solution leakage due to the creeping phenomenon.

In order to make more explicit the effect of the present invention. a leakage acceleration test was con ducted on each gasket. In the testing. the mercury cells of the construction shown in FIG. i, each having a diameter of 15.6 mm and a height of 6.0 mm and comprising each of the insulating gaskets made in the Examples given above. were stored in an environment of a humidity of percent RH or higher. and the external leakage of the electrolyte solution and the capacity of each cell were checked from time to time at a predetermined interval. The leakage was determined by the alkali reaction occurring on litmus paper in contact with the outer surface of the cell. For each gasket. I00 sample cells were submitted for the testing. The results of the testing are shown in Table 3.

Table 3 Percentage of cells yielding electrolyte solution leakage (Z Period of storage twcckl Emimple Z 4 (1 R l l2 l4 lb lb 21) I32 24 1) ll 23 53 us 100 2 ll 21 39 70 95 mo .1 u u u u u 2 3 In H (1x 82 97 4 u u u u o 3 5 is 41 74 as too 5 o o u u o (I 3 S 27 Si 7i s5 6 n o (I u t) 1 2 4 3| 5: 87 mu 7 u o u I) 2 4 7 41 73 ll um s u o o u 3 5 12 23 56 as IOU As shown. the cells comprising the insulating gaskets Other additives include. besides the carbon black of Examples l and 2 showed leaking electrolyte solul5 mentioned in the Examples, silica and clay which can tion already after storage for 4 weeks. and [00 percent be used as reinforcing agents. These additives are used of them showed leaking electrolyte solution after the in the range of -50 parts by weight per 100 parts of lapse of l2-l4 weeks. As contrasted. the cells compristhe halogenated butyl rubber. Vulcanizers. such as teting the gaskets of this invention showed leaking elecramethylthiuram disulfide. zinc oxide and magnesium trolyte solution only after the lapse of tl-IZ uceks. This O ide. are used in the range not larger than 10 parts by mums hat h ll comprising h gaskets f hi i weight. and lubricants, such as stearic acid. in the range vention have a preservable life 2 to 3 times longer than not larger than 5 parts by weight. that ofthe conventional cells. An increasing amount of Allhough the Present invention has been described the electrolyte solution leaking from the cell causes illustrated herein 115 pp to mercury cellsit electrical shorting of the cell or a capacity lowering of 25 Should he understood that invention is Similarly p the n due to a Shmmge 0f the electrolyte Solution plicable to other batteries comprising alkaline electroand also causes corrosion of an equipment in which the y Solutions- Such as manganese dloxide'zlnc alkaline cell is used. Therefore. the prevention of the electrolyte Cells and Closed nlckel'cadmium alkaline Storage solution leakage is the most important problem for the f ll Should also understood h Construc' alkaline cells. According to the present invention. alkat the l l whlch mvemlon l line cells having long preservable lives can be obtained cab: f to Ihul sjhown m the drawmg but as illustrated in the Examples given abovemany modifications are possible. for example. by mak- The insulating gaskets of the invention are made of "l thg l case u dnuble'wall Slrucwre or usmg resin compositions comprising a halogenated butyl rub Smgle j ber. such as chlorinated butyl rubber or brominated what ls cla'lmed butyl rubber as the main constituent. and suitable An l l clj'mpnsmg a metal 62,158 comam amounts of styrenic resin and phenolic resin incorpomg elecmclty'ge,nemtmg elements g metal rated in the halogenated butyl rubber have the effects plate 'l the end of sand case and of imparting the optimum impact resilience and hardmulmmg gaske} mm-Fused l the and of ness to the gaskets made of the composition. lowering 40 smd and saldlialmg gasket hemg made the compressive permanent set factor of the gasket and of resm compo smon a halogefmed, butyl producing a g bond between he packing and the rubber as the constituent and styrenic resin and metal of which the cell case or sealing plate is made. d g i l fi q f l l h h The gaskets of the invention are capable of preventin k ig ii gz fz g 333322 511 :2; the leakage of electrolyte solution. presumably because i muted but 1 rubber apstyrenic resig andga the styrenic resin provides a barrier highly effective j resin g p h therein respectivey in an against the creeping phenomenon of the electrolyte soamount of 10:40 pans by weigh and an amount of lution and concurrently the phenolic resin provides 5420 parts y g p 100 parts of said halogenated sealing of the small gap by being swollen suitably by the hutyl mbber alkaline electrolyte solution. Therefore. the leakage 3. An alkaline Cc wording to Claim 2 in which said i rsgg fgi agg ti s i rs i l ig g fi a z halogenated butyl rubber is chlorinated butyl rubber or I L brominate but '1 rubber. i styrenic l' ll becnme? asemla] to 4. An alli aline cell according to claim 2. in which said tam the tpropglrgsmsz (zidlgfislfsilsllllteuz?fticgfng fhgiill SQ henolic resin is selected from the group consisting of COmPOSI alk 'l henol aldeh 'de resin. melamine-modified herenic and phenolic resins incorporated in the resin nolyulgehyde resinylmd xylenflmodified Phenol 5 composition lin varcying amotunts. a: djscribed inflzplgrrghvde res; le 3. lt will we un crstoot rornt e ia rams o H y H v he Lil ie;a g u z fig gzggsgc tg n fgzz i zglgzif; bl) ptolryrilier resin containing a predominant proportion of per pans 0f the halogenated 6 An alkaline cell according to claim 2. in which said As described in Examples 5-8. the styrenic resin is l compflslimn fl Comprises 20-59 puns by not necessarily simple styrene but may be styrenic res- (15 fight of l remforung Agent. "0 more than lo pans ins containing a large proportion of styrene. cg styrenubutadiene copolymer resins. which facilitate the mold-ability of the gaskets.

by weight of a vulcanizer and not more than 5 parts by weight of a lubricant. 

1. AN ALKALINE CELL COMPRISING A METAL CASE CONTAINING ELECTRICITY-GENERATING ELEMENTS THEREIN, A METAL SEALING PLATE SEALING THE OPEN END OF SAID CASE, AND AN INSULATING GASKET INTERPOSED BETWEEN THE OPEN END OF SAID CASE AND SAID SEALING PLATE, SAID GASKET BEING MADE OF A RESIN COMPOSITION COMPRISIING A HALOGENATED BUTYL RUBBER AS THE MAIN CONSTITUENT AND A STYRENIC RESIN AND A PHENOLIC RESIN INCORPORATED THEREIN.
 2. An alkaline cell according to claim 1, in which said gasket is made of a resin composition comprising a halogenated butyl rubber, and a styrenic resin and a phenolic resin incorporated therein respectively in an amount of 10-30 parts by weight and an amount of 5-20 parts by weight per 100 parts of said halogenated butyl rubber.
 3. An alkaline cell according to claim 2, in which said halogenated butyl rubber is chlorinated butyl rubber or brominated butyl rubber.
 4. An alkaline cell according to claim 2, in which said phenolic resin is selected from the group consisting of alkyl phenol aldehyde resin, melamine-modified phenol aldehyde resin and xylene-modified phenol aldehyde resin.
 5. An alkaline cell according to claim 2, in which said styrenic resin is styrene resin or a styrene butadiene copolymer resin containing a predominant proportion of styrene.
 6. An alkaline cell according to claim 2, in which said resin composition further comprises 20-50 parts by weight of a reinforcing agent, not more than 10 parts by weight of a vulcanizer and not more than 5 parts by weight of a lubricant. 